Microfluidic technology has been heralded as the next technological evolution in biological and chemical research, with its promise of faster, more accurate, readily automatable miniaturized experimentation. Many of the advantages of microfluidic experimentation are evident in the marketplace. For example, the Agilent 2100 Bioanalyzer and its menu of microfluidic devices and reagent kits, supplied by Caliper Technologies Corp., provide a versatile experimentation platform for performing a large number of different analyses important to life science researchers. The data produced by these systems is obtained rabidly in a digitized, highly reproducible fashion.
High throughput experimentation has also been addressed by microfluidic products. The Caliper 250 High Throughput Screening System screens large numbers of different samples, e.g., pharmaceutical test compounds, in a continuous flow microfluidic assay format, to identify potential therapeutic agents from those test compounds. Such systems have the capacity to perform thousands and tens of thousands of assays per day on a single microfluidic device, increasing the throughput of the process while decreasing the footprint and volume of reagents used as compared to conventional screening systems.
While microfluidic systems have been delivering on their promises, the interconnected nature of microfluidic channel networks in the developed systems has led to some limitations of the operability of those systems. By way of example, initial microfluidic systems employed completely electrokinetically driven flow systems. These systems provided precision controllability of fluid and other material movement in all of the interconnected channels of the device, all while moving materials with a flat plug flow profile, with diffusion limited dispersion. However, the use of electric fields to drive material movement also drove electrophoretic separation or biasing of differentially charged species within the channels of the device, yielding data that required more complex data deconvolution. Further, such electrokinetic flow systems also provided slower movement of materials that could reduce throughput where long channel distances were to be traversed. The use of pressure based flow in microfluidic systems results in non-biased movement of differentially charged materials, but creates more highly dispersed flow profiles, resulting from increased Taylor-Aris dispersion in systems that have parabolic flow.
It would generally be desirable to provide microfluidic systems that are optimized to take advantage of the positive aspects of each type of flow profile while eliminating or minimizing the less attractive features of each profile. The present invention meets these and a variety of other needs.